An electromechanical steering system may have an electric servomotor that drives a worm shaft that meshes with a worm wheel arranged on an input shaft of a steering gear, wherein the worm wheel is operatively connected to an input shaft of the steering gear, and wherein the worm shaft and the input shaft are mounted rotatably in a gear housing. The worm shaft and the input shaft may be mounted here in a single, common housing, but also in a multipart gear housing or even in a plurality of gear housings.
A servo steering system of this type imposes relatively high demands on the exactness of the components. In particular, the toothing engagement of the worm wheel and of the worm shaft has to be as precise as possible in order to ensure good transmission of force and torque with little production of noise. Furthermore, constantly changing rotational movements should be anticipated in steering systems, which rotational movements have to be correspondingly transmitted without play by a gear of this type.
A multiplicity of such gears are known, for example from DE 10 2010 003 727 A1, DE 10 2010 002 285 A1 and EP 2 423 075 A2. In general, a multiplicity of these power steering boosts contain means for compensating for the axial or radial play of the toothing engagement by means of springs, wherein it can also be provided, as disclosed in DE 10 2010 002 285 A1, to eliminate a large portion of the play or a basic play by means of a readjustment device and to compensate for remaining residual plays or alternating loadings by corresponding cushioning.
It is known from laid-open application DE 198 24 382 A1 to adjust a fundamental play in a previously described gear once during the installation and then to set same.
The abovementioned measures for adjusting the play between the tooth flanks in the geared engagement require a high technical outlay in order to optimally configure the toothing engagements and to optimally match the toothings to one another. For this purpose, very exacting tolerances have to be maintained, which lead to high costs.
DE 10 2010 002 285 A1 furthermore discloses the possibility of using a plastics toothed ring for the worm wheel. Plastics toothings of this type are used in order to damp impact noises and to introduce a certain degree of elasticity into the system so that possibly present tolerance fluctuations can be compensated for. In the case of electric servo steering systems, the forces which act on the tooth flanks are, however, of such a high magnitude that a correspondingly high degree of wear of the plastics toothing has to be taken into account if the damping properties are actually intended to be used. Alternatively, use can be made of solid plastics in which, however, the desired dampings do not occur during operation.